The ornamental design for a cushiondevice, as shown and described.
FIG. 1 is a perspective view thereof;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is an exemplary diagram of the use of the cushion device thereof, the broken lines depict environmental subject matter only and form no part of the claimed design.